Codeposition of a metal and fluorocarbon resin particles

ABSTRACT

FINE PARTICLES OF FLUOROCARBON RESINS SUCH AS TEFLON PARTICLES CAN BE READILY CODEPOSITED WITH METALS WHEN THEY ARE DISPERSED IN AQUEOUS PLATING BATHS, WHEN THERE IS ALSO PRECENT IN THE BATHS A FLUOROCARBON SURFACTANT SUCH AS PERFLUORO N-OCTANOIC ACID, PERFLUORO N-OCTYL SULFONIC ACID, PERFLUORO P-ETHYL CYCLOHEXYL SULFONIC ACID, OR THEIR SALTS. SUCH 2-PHASE COMPOSITE PLATES HAVE GOOD ANTI-SEIZING AND ANTI-FRICTION PROPERTIES.

United States Patent 3,677,907 CODEPOSITION OF A METAL AND FLUORO-CARBON RESIN PARTICLES Henry Brown, Huntington Woods, and Thaddeus W.Tomaaewski, Dearborn, Mich., assignors to The Udylite Corporation,Warren, Mich. No Drawing. Filed June 19, 1969, Ser. No. 834,908 Int. Cl.C23b /48, 5/20 US. Cl. 204-16 18 Claims ABSTRACT OF THE DISCLOSURE Fineparticles of fluorocarbon resins such as Teflon particles can be readilycodeposited with metals when they are dispersed in aqueous platingbaths, when there is also precent in the baths a fluorocarbon surfactantsuch as perfluoro n-octanoic acid, pei'fluoro n-octyl sulfonic acid,perfluoro p-ethyl cyclohexyl sulfonic acid, or their salts. Such 2-phasecomposite plates have good anti-seizing and anti-friction properties.

This invention relates to the cathodic codeposition of multitudinousfine particles of fluorocarbon or modified fluorocarbon resins dispersedas fine powders in aqueous electroplating baths containing dissolvedtherein fluorocarbon surface-active agents. It relates especially to thecodeposition of these fluorocarbon resin powders with nickel, cobalt,iron and their binary and ternary alloys, and with copper, silver, goldbrass, lead, and lead-tin and lead-tin-copper alloys from the respectivemetal plating baths containing dissolved therein a fluorocarbonsurfactant.

We have found that fine powders of fluorocarbon resins when dispersedfor example in a Watts nickel bath will not appreciably codeposit onvertical surfaces unless a fluorocarbon surface-active agent is alsopresent in the bath. It is necessary to have a fluorocarbonsurface-active agent dissolved in the aqueous electroplating bath beforeit is possible to densely codeposit the fine particles of thefluorocarbon resins on vertical surfaces.

Fluorocarbon solid surfaces have the lowest coefficient of friction ofany solid. This is due to their extremely low surface energies orsurface tensions. Therefore the incorporation of multitudinous particlesof fluorocarbon resins in the electrodeposited surfaces of nickel,cobalt, iron, copper, lead, lead-tin, brass, silver, bronze, etc. leadsto surfaces which have excellent anti-seizing properteis and goodlubricity even when dry. Teflon particles (polytetrafluoroethylene),modified Teflon such as VydaX (which is a fluorocarbon telomer), Kel-Fpowder (polytrifluorochloroethylene) are examples of fluorocarbon ormodified fluorocarbon powders which can be obtained in a finely dividedstate. The important factor for obtaining the maximum in dry lubricationand anti-seizing properties is a high volume percent of the codepositedparticles. Also, it is important that these fluorocarbon resin powderscontain a prepondenace (over 50%) of fluoro groups attached to thecarbon atoms of the polymeric resins. Thus, chloro groups, or oxygen oroxygen containing groups or hydrogen or nitrogen containing groups canbe present, but as relatively minor constituents.

The particle sizes of the powders that codeposit from the nickel, nickelalloy, copper, lead, lead-tin, etc. aqueous electroplating baths rangefrom about 2 to 3 mils down to submicroscopic particles. Often there arecoarser resin particles present in the dispersed powders in the platingbaths, but these do not readily codeposit on vertical surfaces. It wasalso found that in general, it was advantageous to wash the fluorocarbonresin powders with isopropyl alcohol before mixing them into the plat-3,677,907 Patented July 18, 1972 ing baths containing the dissolvedfluorochemical surfaceactive agents. This step aided the rapid wettingof the fluorocarbon resin powders by the fluorocarbon sufactants.

These fluorocarbon resin powders codeposit on vertical surfaces as wellas on shelf areas with the most uniform codeposition occurring with thefinest powders even with very thin plate of 0.05 to 0.1 mil thicknesses.However to plate out a maximum of the particles of 0.1 mil to 2 mils(2.5 to 50 microns) sizes, thicknesses of plate of 0.1 mil to about 0.5or even to 1 mil thicknesses should be used. The formation of a denselypopulated metal surface with codeposited resin particles persists withcontinued plating past 2 mils thicknesses with consistent codeposition.

The plating solutions of the present invention are metal plating bathsin which the fluorocarbon resin particles are dispersed and which alsocontain, in addition to the metal ions to be plated, at least onefluorocarbon surfactant. These solutions may be electroplating baths forplating nickel, cobalt, iron, the binary and ternary alloys of these,copper, silver, gold, brass, lead, lead-tin or leadtin-copper alloys,and the like. Such plating baths are conventional and Well known tothose in the art.

It is desirable that such baths contain the fluorocarbon resin particlesin an amount of at least about 1 gram/ liter, and preferably in anamount of about 2 to grams/ liter. The fluorocarbon surfactant isdesirably present in the bath in an amount of at least about 0.01 grams/liter and preferably in an amount within the range of about 0.01 to 5grams/ liter. Various fluorocarbon surfactants may be used so long asthey are soluble in the plating baths and are not detrimental to theplating of the fluorocarbon resin particles and/or the metal. Examplesof some of the fluorocarbon surfactants which may be used to obtain adense codeposition of the resin particles with the metal are given inTable I.

TABLE I Fluorocarbon Surface-Active Agents 1) pertluorocyclohexylsulfonic acid F S 0 H (Na, +K, 0.150., salt) 0 Fa- S 0 11 C 2 F5 F -S03H 5) C F3 C F3 Que...

F 0 F 0 F28 03H 9) O F-,\(C Fa -C F28 0311, where n=28 10 01c 1*.(0F2)nC F28 0311 11 omo rot-o rzcoon 12 ClCF2(CF2)nCFaCOOH 13) 01 0maroon-o F20 OOH 14 no FAG F2)nC F20 OOH 15 norztoro -o F21 o on 2 16)no mo Fa -onto s 0,11

) armor) ori lon 16 3 2 2 3 0- 18) ergo Fa -ch ornltoozrn 011 19 0 mo ra-o H2NH2HC1 In some cases it is desirable to use the normal hydrocarbonsurfactants together with the fluorocarbon surfactants. For example, inthe acidic type of nickel baths, like the Watts bath or the highchloride nickel bath, the fluorocarbon surfactants, even though theylower the surface tension more than the best type of hydrocarbonsurfactants for nickel and nickel alloy baths, they do not preventhydrogen gas pitting. That is, the fluorocarbon surface-active agents donot have detergent properties for the usual types of organiccontamination (dust, traces of organic materials from vat linings, etc.)that may cause hydrogen gas bubbles to stick to the cathode, thuscausing pitting in the cathode. The usual hydrocarbon surfactants fornickel plating such as sodium 2-ethyl hexyl sulfate, and sodium n-octylsulfate to sodium lauryl sulfate, solubilize in their micelles theordinary hydrocarbon type impurities, unlike the micelles of thefluorocarbon surfactants. However, the fluorocarbon surfactants areunique in their ability to Wet the fluorocarbon resin particles, andmake possible the extensive codeposition of the dispersed fluorocarbonpowders.

In some cases it is also desirable to codeposit inorganic bath-insolubleline particles such as barium sulfate or strontium sulfate or mica alongwith the fluorocarbon resin particles, in order to add strength to thecomposite plate, Without decreasing the high lubricity and antiseizingproperties of the plate. In fact, just the dense codeposition ofparticles such as barium or strontium sulfate provides very importantlubricity and anti-stick properties, because of the slip qualities ofthese particular powders. However, if over about 50 g./l. of bariumsulfate is used in the baths containing about 50 g./l. of thefluorocarbon dispersed particles, then the codeposition of the bariumsulfate particles will predominate over fluorocarbon particles.

When air agitation is used to keep the particles dispersed in the bath,the shorter chain surfactants in general are preferred to avoidover-foaming. With mechanical agitation, the longer chain surfactantscan be used as Well as the shorter chain types. The use of anti-foamingagents is generally not desirable, but certain ones, like octyl alcoholcause no troubles.

In the case of acid copper plating baths it is also necessary to havepresent in the bath besides a fluorocarbon surfactant, a promoteraddition agent to cause the extensive codepos'ition of the fluorocarbonresins on vertical surfaces. The promoter addition agents for the acidcopper plating baths are salts of monovalent cations such as those ofthallium, cesium, rubidium, sodium, potassium, ammonium, lithium,amines, especially aliphatic polyamines or imines, such as tetraethylenepentamine, or amino acids such as alanine, or EDTA. Actually the use ofamino acids and especiall chelating agents of the type of EDTA help inthe codeposition of the fluorocarbon particles not only in acid copperplating baths where they are the most helpful, but also in zinc sulfatebaths, nickel plating baths, alkaline cyanide silver and copper platingbaths, in brass plating baths, and in pyrophosphate copper platingbaths.

Below are listed some examples of electroplating baths for codepositingfluorocarbon resin particles with metals.

EXAMPLE I Concentration in grams per liter NiSO -6H O 200-300. NiCl -6HO 40. Teflon particles (1 micron to about 50 microns particle size)30-100. Perfiuoro p-ethyl cyclohexyl sulfonic acid 0.1-2. p-Toluenesulfonamide 0-2. Benzene sulfonamide 0-2. o-Benzoyl sulfimide 0-2.S-Methoxy coumarin 0-0.5. Temperature-l00 to 160 F pH 2.5-5.2. Cathodecurrent density 20-60 amps/sq. ft. Air agitation.

EXAMPLE II Concentration in grams per liter CuSO -5H O -250. H 80 5-100.Teflon particles (1 micron to about 50 microns particle size) 2-150.

Perfluoro n-octyl sulfonic acid 0-0.01. Perfiuoro p-ethyl cyclohexylsultonic acid 0.1-2. EDTA 5-20. Temperature-60 to F. Agitation-air ormechanical. Cathode current density 10-100 amps/sq. ft.

EXAMPLE III High cathode efliciency brass bath (90%+) Concentration ingrams per liter Perfluoro ammonium n-octanoate or Perfiuoro potassiump-ethyl cyclohexyl sulfonate 0.5-2. Temperaturel70 to F. Cathode currentdensity 10-40 amps/sq. ft.

Mild air agitation or gentle mechanical agitation.

The above brass bath yields about an 80-20 copperzinc brass alloy platewith the codeposited Teflon particles present. By using different ratiosof copper to zinc, it is possible to deposit higher zinc alloy brassessuch as 70-30 and 60-40 copper-zinc brasses. Also by adding smallconcentrations of lead carbonate or lead acetate to the baths, it ispossible to incorporate a small percentage of lead into the brassdeposits which also helps in anti-friction applications.

The electroplating baths for the codeposition of the fiuorochemicalresin particles should have relatively high cathode efficiencies,cathode efliciencies of at least about 90% being preferred.Additionally, however, electroless (electrodeless) copper or nickel orcobalt (or the alloys of the iron group) plating baths, which alsoincorporate fluorocarbon resin particles and the fluorocarbonsurfactants, such as perfluoro p-ethyl cyclohexyl sulfonic acid or itssalts, may also be used.

EXAMPLE IV By way of example of the use of such electroless baths, abath is formulated containing the following components in the amountindicated:

Concentration in grams/liter Basic nickel carbonate 10. Hydrofluoricacid 6 ml./liter. Citric acid 5.5.

NH HF 10. Sodium hydrophosphite 20. Ammonium hydroxide 30 ml./liter.

To this bath was added the Teflon particles and fluorocarbon sufactantas in Example I and the bath was operated at a temperature of from170-180 F. to obtain a codeposit of Teflon particles and electrolessnickel plate on a steel surface immersed therein.

EXAMPLE V The following baths were formulated with the components and inthe amounts indicated:

To each of these baths was added the Teflon particles and fluorocarbonsurfactant as in Example I. The baths were then operated under thefollowing conditions of codeposit the respective metals and Teflonparticles, as in Example I:

Temperature 120-150 F. Current density up to amp/sq. ft. Gold or steelanodes.

Acid gold baths operated at pH values from 3-6 may also be used insteadof alkaline ones, for example:

Gold 4-12 g./l. Citrates 90 g./l. pH 3-6. Cathode current densitylamps/sq. ft. Anodes carbon or platinum.

Temperature 60-100 F. Cathode current density amps/sq. ft. Lead-tinalloy anodes.

Temperature 70-80 F. Current density 5-15 amps/sq. ft.

Silver anode.

What is claimed is:

1. A method of electroplating which comprises codepositing dispersedfine fluorocarbon resin particles with a metal from an aqueous metalplating bath having cathode efficiencies higher than about and havingdissolved in said plating bath a fluorocarbon surfactant in aconcentration of at least about 0.01 gram/liter, and having at least 1gram/liter of the fluorocarbon resin particles dispersed in the metalplating bath.

2. A method in accordance with claim 1 wherein said fluorocarbon resinparticles are essentially polytetrafluoroethylene of particle size lessthan about 50 microns.

3. A method in accordance with claim 1 wherein said fluorocarbonsurfactant is essentially perfluoro n-octyl sulfonic acid in aconcentration of 0.01 to 1 gram/liter.

4. A method in accordance With claim 1 wherein said fluorocarbonsurfactant is perfluoro p-ethyl cyclohexyl sulfonic acid in aconcentration of 0.05 to 2 grams/ liter.

5. A method in accordance with claim 1 wherein said metal plating bathis essentially an acidic nickel electroplating bath.

6. A method in accordance with claim 1 wherein said metal plating bathis an alkaline silver electroplating bath.

7. A method in accordance with claim 1 wherein said metal plating bathis essentially an electroless nickel plating bath.

8. A method in accordance with claim 1 wherein said metal plating bathis essentially a gold electroplating bath.

9. A method in accordance with claim 1 wherein said metal plating bathis essentially a lead-tin alloy electroplating bath.

10. An aqueous metal plating bath comprising a plating bath of cathodeefliciency greater than about 90% and containing dispersed therein atleast 1 gram/liter of fine fluorocarbon resin particles and havingdissolved in said plating baths a fluorocarbon surfactant in aconcentration of at least about 0.01 gram/liter.

11. A bath in accordance with claim 10 wherein said fluorocarbon resinparticles are essentially polytetrafluoroethylene of particle size lessthan about 50 microns.

12. A bath in accordance with claim 10 wherein said fluorocarbonsurfactant is essentially perfluoro n-octyl sulfonic acid in aconcentration of 0.01 to 1 gram/liter.

13. A bath in accordance with claim 10 wherein said fluorocarbonsurfactant is perfluoro p-ethyl cyclohexyl sulfonic acid in aconcentration of 0.15 to 2 grams/ liter.

14. A bath in accordance with claim 10 wherein said metal plating bathis essentially an acidic nickel electroplating bath.

15. A bath in accordance with claim 10 wherein said metal plating bathis an alkaline silver electroplating bath.

16. A bath in accordance with claim 10 wherein said metal plating bathis essentially an electroless nickel plating bath.

17. A bath in accordance with claim 10 wherein said metal plating bathis essentially a gold electroplating bath.

18. A bath in accordance with claim 10 wherein said metal plating bathis essentially a lead-tin alloy electroplating bath.

References Cited UNITED STATES PATENTS 3,434,942 3/ 1969 Waterman 204-38R 2,820,752 l/1958 Heller 204-181 3,506,555 4/1970 Stadler et a1.204-181 3,461,044 8/ 1969 Lyons et a1 204-38 R 3,403,089 9/ 1968 Joyce204181 3,356,467 12/1967 Brown 204-41 3,175,964 3/1965 Watanabe et a1204-181 2,530,366 11/1950 Gray 204-181 (Other references on followingpage) 7 8 UNITED STATES PATENTS The Co-Deposition of Copper andGraphite, 1. Electro- 5 2 1 6/1971 Hovey et 1 204-42 chem. $06., 541928, by Fmk 1 31., pp. 315-316. 3,539,489 11/1970 Ness 204-481 I 3 497440 2 1970 weigel 204 181 JOHN MACK Primary Exammer 5 R. L. ANDREWS,Assistant Examiner OTHER REFERENCES Electrophoretic Deposition,Kirk-Othmer Encyclqpedia of Chem. Technology, 2nd ed. 1965, vol. 8, pp.27, 106-1; 204-43, 46, 48, 52 R, 181 31, 32.

